The present invention relates to fluid engines and, more particularly, to pneumatic engines adapted for use in toys such as aeroplanes and wheeled vehicles, including toy cars, trucks and trains. The invention is, particularly, directed to a piston-operated pneumatic engine. Accordingly, the only prior art relative thereto known to the inventor is that of U.S. Pat. No. 4,329,806 (1982) to Akiyama, entitled Fluid Engine, and the engine of an unpatented compressed air operated model aeroplane sold in the United Kingdom in or about 1990 known as the Jonathan, utilizing a so-called Z-model engine.
Addressing, firstly, the above reference to Akiyama, it differs, from that of the present invention in a number of material respects, these including differences in the respective input and exhaust mechanisms and in the relationship of the engine piston to the air inlet means to the interior of the engine cylinder. More specifically, Akiyama does not teach or indicate the possibility of a spring enhanced piston action, much less one for providing pressurized air input control to the engine cylinder.
With respect to the Jonathan device known in the United Kingdom, the same constitutes a direct predecessor of the instant invention which, however, differs therefrom in a number of respects and as such provides a far less efficient pneumatic engine for use with toy vehicles such as an aeroplane. More particularly, the Jonathan has two distinct modes of operation, one a high pressure mode when the air tank or air pressure canister thereof is at high pressure and a second mode when the air canister is at low pressure. Such a distinction between high and low pressure operations does not exist in the present invention.
Further, the Jonathan employs a piston diaphragm which constitutes the primary air input control means of that system. In distinction, the present system employs a one-way check valve which selectively co-acts with the piston to control air flow through the system intake manifold. Further, the Jonathan possesses two different exhaust channels, one in the lower cylinder housing and the other in the upper cylinder housing. In distinction, the instant system employs a single plurality of air exhaust apertures, all situated in the upper or proximal region of the cylinder housing.
More generally, the Jonathan does not afford efficient use of compressed air stored within the inflatable air canister and, as such, cannot achieve a comparable period of operation to that of the present invention. That is, to maintain operation of the system when the canister air pressure falls below a certain level, requires a distinct mode of engine operation during intervals of reduced pressure.
While the Jonathan, like the instant invention, makes use of a spring to enhance performance of the engine piston, the length and radius of the spring differ materially from that of the invention. Thereby, the Jonathan cannot optimally use the potential energy resident in the compressed air as it passes through the intake manifold into the engine cylinder housing. Also, the spring itself cannot contribute to system deficiency in the manner of the present invention.
It is noted that the use of compressed air power as a motive force for model aeroplanes and model vehicles has, in one form or another, existed in the art since approximately 1920. In such devices, so-called air motors which were constructed from brass and employed a three-cylinder arrangement for purposes of balance. The limiting factor in this technology was the air reservoir which, prior to the advent of contemporary plastics, was of necessity metallic. Such metal reservoirs, while having significant weight relative to the weight of the model aeroplane also did not possess properties of elasticity and resilience resident in modern plastics as, for example, exists today with two or three liter soda bottle. Accordingly, with the advent of a lightweight plastic soda bottle, a practical air container or canister, for use in a compressed air or pneumatic power plant for a so-called fluid expansion engine appeared. Thereby, the above-referenced invention of Akiyama marketed by Tome Kogyo Company of Japan and the Jonathan device with its Z-engine became possible.
The present invention may thereby be appreciated as a continuation of this process of development of compressed air and expansion pneumatic engines usable with a variety of toy vehicles including toy aeroplanes.